Coronary stenting: why size matters

In Silico Evaluation of In Vivo Degradation Kinetics of Poly(Lactic Acid) Vascular Stent Devices

Biodegradable vascular stents (BVS) are deemed as great potential alternatives for overcoming the inherent limitations of permanent metallic stents in the treatment of coronary artery diseases. The current study aimed to comprehensively compare the mechanical behaviors of four poly(lactic acid) (PLA) BVS designs with varying geometries via numerical methods and to clarify the optimal BVS selection. Four PLA BVS (i.e., Absorb, DESolve, Igaki-Tamai, and Fantom) were first constructed. A degradation model was refined by simply including the fatigue effect induced by pulsatile blood pressures, and an explicit solver was employed to simulate the crimping and degradation behaviors of the four PLA BVS. The degradation dynamics here were characterized by four indices. The results indicated that the stent designs affected crimping and degradation behaviors. Compared to the other three stents, the DESolve stent had the greatest radial stiffness in the crimping simulation and the best diameter maintenance ability despite its faster degradation; moreover, the stent was considered to perform better according to a pilot scoring system. The current work provides a theoretical method for studying and understanding the degradation dynamics of the PLA BVS, and it could be helpful for the design of next-generation BVS.

How to deal with vessel diameter mismatch in left main bifurcation stenting

Left main coronary artery percutaneous coronary intervention is particularly complex when stenting across the distal bifurcation is required in the presence of a diameter mismatch between the proximal main and distal branches. A suboptimal procedural result increases the risk of thrombosis and restenosis. Considering the paucity of data published on this topic, our objective was to provide technical solutions to deal with this complex anatomy. We described four cases showing the use of devices and techniques which allowed us to overcome a diameter discrepancy between adjacent coronary segments: (1) self-expanding nitinol stent; (2) stent platform with noteworthy expansion capacity; (3) the 'extended skirt' technique; (4) the 'trouser-leg' technique. In conclusion, the use of specific strategies and devices allows a safe and effective approach to be used to perform treatment that respects the coronary anatomy, and to optimize percutaneous coronary intervention results in complex scenarios.

The Effect of Clinical Characteristics and Stent Parameters on Left Ventricular Mechanical Dyssynchrony

Aim. To study short term effect of stent size and number on left ventricular mechanical dyssynchrony after elective percutaneous coronary intervention (PCI) to left anterior descending (LAD) artery.

Materials and methods. the study included 150 adult patients with LAD lesion treated with PCI using drug-eluting stent. Patients were evaluated pre PCI then 1 month and 3 months post PCI for evaluation of mechanical dyssynchrony using tissue synchronization image (TSI).

Results. Before revascularization mean left ventricular ejection fraction was 51.2±5.7 %, mean time to peak TSI was 213.6±10.9 ms; 1 month after PCI TSI improved significantly to 163.7±17.6 ms (p<0.001), 3 months after PCI showed more improvement to 120.7±26.9 ms (p<0.001). After 3m; 61 patients (40.7%) showed recovery to normal TSI value. The predictors of non-improvement of time to peak TSI after 3 months were diabetes mellitus (p=0.007), dyslipidemia (p=0.001) and stent length (p=0.001), number of stents (p=0.004). There were strong negative correlation between stent length and improvement of the time to peak TSI at 1 month (r=-0.352, p<0.001) and at 3 months (r=-0.509, p<0.001),and also with number of stent at 1 month (r= -0.173, p=0.034) and at 3 months (r=-0.499, p<0.001), but the correlation between stent diameter and improvement of the TSI wasn’t significant neither at 1 month nor at 3 months (r=0.055, p=0.504 and r= -0.018, p=0.827) respectively.

Conclusion. Increased number and length of the implanted stents were predictors to non-improvement of mechanical dyssynchrony, while stent diameter didn’t affects the recovery.

Patient eligibility for application of a two-filter cerebral embolic protection device during transcatheter aortic valve implantation: does one size fit all?

OBJECTIVES

This study sought to determine the percentage of patients potentially eligible for implantation of the Sentinel™ Cerebral Protection System (Sentinel-CPS) during transcatheter aortic valve implantation (TAVI) and to identify the reasons for treatment exclusion.

METHODS

We retrospectively performed an analysis of pre-TAVI multislice computed tomography (MSCT) aortograms and data review of all patients undergoing a TAVI procedure in 2017 (n = 317). MSCT evaluation included the assessment of aortic arch anatomy and the vascular dimensions of the brachiocephalic and left common carotid artery. Data analysis focused on comorbid conditions, precluding 6-Fr sheath radial access and filter deployment due to history of previous artery interventions.

RESULTS

MSCT and data analysis showed Sentinel-CPS compatibility in 61.5% of patients (n = 195). Sentinel-CPS would have been contraindicated in 38.5% (n = 122) due to one or more of the following: (i) measured diameters of the filter-landing zones <9 or >15 mm in the brachiocephalic artery and <6.5 or >10 mm in the left common carotid artery (n = 116; 88 with carotid dimensions too small); (ii) significant subclavian artery stenosis (n = 4) or an aberrant subclavian artery (n = 3) precluding Sentinel-CPS implantation and (iii) clinical characteristics including hypersensitivity to nickel-titanium (n = 1), radial artery occlusion (n = 1) or previous left common carotid artery interventions (n = 5).

CONCLUSIONS

MSCT and clinical data supported Sentinel-CPS compatibility in 61.5% of patients. The most common reason for treatment exclusion was inappropriate diameter within the target landing zone of the left carotid artery. Future device development should address this limitation.

A Study of Coronary Bifurcation Shape in a Normal Population

During percutaneous coronary intervention, stents are placed in narrowings of the arteries to restore normal blood flow. Despite improvements in stent design, deployment techniques and drug-eluting coatings, restenosis and stent thrombosis remain a significant problem. Population stent design based on statistical shape analysis may improve clinical outcomes. Computed tomographic (CT) coronary angiography scans from 211 patients with a zero calcium score, no stenoses and no intermediate artery, were used to create statistical shape models of 446 major coronary artery bifurcations (left main, first diagonal and obtuse marginal and right coronary crux). Coherent point drift was used for registration. Principal component analysis shape scores were tested against clinical risk factors, quantifying the importance of recognised shape features in intervention including size, angles and curvature. Significant differences were found in (1) vessel size and bifurcation angle between the left main and other bifurcations; (2) inlet and curvature angle between the right coronary crux and other bifurcations; and (3) size and bifurcation angle by sex. Hypertension, smoking history and diabetes did not appear to have an association with shape. Physiological diameter laws were compared, with the Huo-Kassab model having the best fit. Bifurcation coronary anatomy can be partitioned into clinically meaningful modes of variation showing significant shape differences. A computational atlas of normal coronary bifurcation shape, where disease is common, may aid in the design of new stents and deployment techniques, by providing data for bench-top testing and computational modelling of blood flow and vessel wall mechanics.

Effect of oversized partial postdilatation on coatings of contemporary durable polymer-based drug-eluting stents: a scanning electron microscopy study

BACKGROUND

 Oversized postdilation of drug-eluting stents (DES) is often performed to avoid stent malapposition. In stents implanted in long lesion or major bifurcations, extremely oversized partial postdilation may be required, which exposes DES coating to extreme forces. This study aims to assess shape and incidence of coating irregularities on durable polymer-based DES following extremely oversized partial postdilatation.

METHODS

 Fifteen DES samples (3 3.5 mm stents of Cypher Select plus [Cordis Europa, Roden, the Netherlands], Taxus Liberté[Boston Scientific Corp., Natick, MA, USA], Endeavor Sprint [Medtronic Vascular, Santa Rosa, CA, USA], Endeavor Resolute [Medtronic Vascular, Santa Rosa, CA, USA], and Xience V [Abbott Vascular, Santa Clara, CA, USA]) were deployed in sterile water (37 °C) at 14 atm, followed by a proximal postdilation with noncompliant 5.0-mm balloons at 18 atm. Stents were then examined with scanning electron microscopy.

RESULTS

 Thorough examination of a total of 660 scanning electron microscopic images demonstrated that shape and incidence of coating irregularities in the postdilated and/or transitional DES regions differed only mildly from the nonpostdilated regions. Cypher Select plus showed more peeling without bare metal aspect in the postdilated and transitional regions, and cracks were wider (P < 0.001) in the postdilated and transitional regions; in Taxus Liberté one additional irregularity (torn webbing) and more wrinkles were observed (P < 0.05 for both); in Endeavor Resolute wider cracks were found in the extremely postdilated region only (P < 0.001). Endeavor Sprint and Xience V showed no differences in shape or incidence of coating irregularities between oversized and nonoversized stent regions.

CONCLUSIONS

 Bench side assessment of five contemporary durable polymer-based DES with scanning electron microscopy suggests that even very aggressive stent postdilatation results in no more than mild differences in coating irregularities between postdilated and nonpostdilated stent regions.